Well, you can make it mandatory, the same way some countries require cattle vaccination, and other things. In the end it should be more acceptable to general public than just forbidding them to eat beef. And the seaweed shouldn't be too expensive, after all it is "weed".

And with more research they possibly could isolate that one tiny chemical substance from seaweed that does all the work here, and synthesize it, so we can produce it cheaply?